My VERY TRAUMATIZED lone chickie

Recently, we received 4 Black Sex Link hens, approximately 6 weeks old. They loved their secure hen house and outside pen. We used to have Rhode Island Reds with a rooster that was satin reincarnated. We gave the rooster away when the last of our RIR had passed from age. One morning, we found one of the chicks was missing and immediately checked everything to make sure it was secure...mystery unsolved. The next morning, unfortunately, two more of our chicks went missing. We finally figured out the predator was a racoon. Since then, we have been taking her to our guest bathroom with a stepstool where she can perch at night (she will not go back into the hen house where she was traumatized for her food and water). We, finally moved it to the outside pen where she spends her days alone. Because she is by herself right now, does any one know how long she may have the terrible memories of her sisters being taken so violently and will having new chickies help her? I feel so helpless in trying to communicate to her that everything is now safe and secure and that we care and love her.

We had the exact same issue. Unfortunately, our last chickens were taken by the raccoon as well and we have started over with four pullets... I'd say definitely get company for her. Additionally, you should thoroughly clean out your coop and put extra security in place so it does not happen again. Once that is done, she should be okay with returning to the coop.
Edited to add: I second the advice to set traps and keep setting them!